Cooling plate for an iron- or steelmaking furnace

ABSTRACT

A cooling plate for an iron and steelmaking furnace includes a copper cooling plate body having at least one cooling duct for a cooling medium extending essentially parallel with the back of the cooling plate body. The cooling plate body further includes a preformed, externally accessible recess into which the cooling duct opens. A connection piece is utilized as a cooling medium connection on the back of the cooling plate body, while a formed piece fitted within the externally accessible recess forms a deflection surface for the cooling medium flowing from the connection piece into the cooling duct, or from the cooling duct into the connection piece.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of International ApplicationNo. PCT/EP1999/08735, filed on Nov. 12, 1999, Luxembourg PatentApplication No. LU 90328, filed on Dec. 16, 1998 and is a Divisionalapplication of U.S. Non-Provisional Application No. Ser. No. 09/868,117,filed on Aug. 20, 2001, now U.S. Pat. No. ______.

FIELD OF THE INVENTION

The invention relates to a cooling plate for an iron- or steelmakingfurnace.

BACKGROUND OF THE INVENTION

Such cooling plates are arranged on the inside of the furnace shell andhave internal cooling ducts. These cooling plates are connected viaconnection pieces projecting from their back to a cooling system of theshaft furnace outside the furnace shell. Their surface facing theinterior of the furnace is generally lined with a refractory material.

Most of these cooling plates are still made from cast iron. As copperhas a far better thermal conductivity than cast iron; however, there isa current trend towards the use of cooling plates made from copper orcopper alloys. Meanwhile, several production methods have been proposedfor copper cooling plates.

Initially, an attempt was made to manufacture copper cooling plates bymould casting like cast iron cooling plates, the internal cooling ductsbeing formed by a sand core in the mould. This method has not provedeffective in practice; however, because the cast copper plates exhibitcavities and porosity far more frequently than cast iron cooling plates.However, it is well known that such cavities and porosity have anextremely negative effect on the life and thermal conductivity of theplates.

It is already known from GB-A-1571789 how to replace the sand core by apreformed metallic pipe coil made from copper or high-grade steel inmould casting of the cooling plates. The pipe coil is integrally cast inthe cooling plate body in the mould and forms a helical cooling duct.The two ends of the pipe coil project as connection pieces from thecooling plate body. This method has also not proved effective inpractice. A high heat transmission resistance exists between the coppercooling plate body and the integrally cast pipe coil, so that relativelypoor cooling of the plate results. Furthermore, cavities and porosity inthe copper can likewise not be effectively prevented with this method.

Copper cooling plates for metallurgical furnaces are known from DE29611704 U1, according to which prefabricated coolant ducts, consistingof copper pipe sockets, copper pipe lines and copper pipe bends areintegrally cast in the cooling plate. The complete, prefabricated copperconduit is placed into the casting mould and the molten copper is pouredaround it. An improvement in heat transmission is expected for as aresult of a partial fusing of the molten copper and the pipe wall.However, this process also fails to provide any protection from cavitiesand porosities in the cast copper plate.

A cooling plate made from a forged or rolled copper ingot is known fromDE-A-2907511. The cooling ducts in this case are blind holes, which areintroduced into the rolled copper ingot by mechanical deep drilling. Theblind holes are sealed by soldering or welding in threaded plugs.Connecting holes to the blind holes are drilled from the back of theplate. Connection pieces for coolant feed or return are subsequentlyinserted in these connecting holes and soldered or welded in. Finally,pipe connection pieces with a larger diameter are welded or soldered asspacers coaxially with the connection pieces on the back of the plate.

The subsequently published WO 98/30345 describes a method in which apreform of the cooling plate is continuously cast. Inserts in thecasting duct of the continuous casting mould produce ducts running inthe continuous casting direction, which form straight cooling ducts inthe finished cooling plate. The cross-section of these integrally castducts preferably has an oblong shape with its smallest dimension atright angles to the cooling duct. Consequently cooling plates with asmaller plate thickness than cooling plates with drilled ducts can bemanufactured. Copper is thus saved and the useful volume of the furnaceincreased. A further advantage of the oblong cross-section is thatlarger exchange areas on the coolant side can be achieved in the coolingplate. A plate is cut out of the continuously cast preform by two cutsat right angles to the casting direction, two end faces with a spacingcorresponding to the required length of the cooling plate being formed.In the next production step connecting holes terminating in the ductsare drilled into the plate at right angles to the rear surface and theend terminations of the ducts closed. Connection pieces are subsequentlyinserted in the connection holes, as already described above.

The methods described in DE-A-2907511 and WO98/30345 both permitproduction of high-grade cooling plate bodies from copper or copperalloys, the method described in WO98/30345 being characterized byparticularly low production costs. However, a disadvantage of thefinished cooling plates of both methods compared to cooling plates withintegrally cast pipe coils or mould-cast plates is that they exhibit arelatively high pressure loss in the area of the transitions from theconnection pieces to the cooling ducts. This applies in particular, butnot exclusively, if the cooling ducts have an oblong cross-section, asdescribed in WO98/30345.

SUMMARY OF THE INVENTION

For the sake of completeness it should also be mentioned that acast-iron cooling plate with integrally cast cooling pipes, which has anoval cross-section in its straight section, but a circular cross-sectionat the inlet and outlet, is described in EP-A-0144578.

The invention is based on the task of creating a transition ensuringrelatively favorable flow from the connection pieces to the coolingducts without the need to revert to mould-cast cooling plate bodies orcooling plate bodies with integrally cast cooling pipes with theirabove-mentioned disadvantages. This problem is solved by a cooling plateaccording to claim 1 or by a cooling plate according to the process ofclaim 16.

The cooling plate according to the invention comprises a copper coolingplate body (i.e. a cooling plate body made from copper or a copperalloy), with at least one cooling duct, which extends essentiallyparallel with the back of the cooling plate. At least one connectionpiece is arranged on the back of the cooling plate body and terminatesin the cooling plate body in the at least one cooling duct. According tothe invention, the cooling plate has a formed piece, which is fitted ina prefabricated, externally accessible recess in the cooling plate bodyand forms a deflection surface for the cooling medium in the area of thetermination of the connection piece in the cooling duct. The entry ofthe cooling medium from the connection piece into the cooling duct orfrom the cooling duct into the connection piece can be improved from theflow point of view in an extremely simple way by this deflectionsurface. Consequently, the pressure losses in the cooling plate can besubstantially reduced, which of course has a favorable effect on theenergy consumption for circulation of the cooling medium. The risk ofsteam bubble formation by high local pressure losses is likewise greatlyreduced. Furthermore, escape of the air during filling of the coolingplates with the cooling medium is simplified by the deflection surfaceaccording to the invention. In other words, the deflection surfacesaccording to the invention prevent air pockets from forming in thecooling ducts and causing so-called “hot spots”. It should also be notedthat the invention can be applied to cooling plate bodies, which aremanufactured by the methods, described in DE-A-2907511 and inWO98/30345, with excellent results with regard to reduction of thepressure losses. Consequently these cooling plate bodies can also beused, if low-pressure losses are required, which was so far notpossible.

In an extremely simple embodiment of the invention, the formed piece isarranged in an axial extension of the cooling duct, the deflectionsurface being formed by one of its end faces. If the cooling duct isformed, for example, by a duct which has an opening in an end face ofthe cooling plate body, the formed piece is advantageously a plug, whichis inserted in this opening and extends into the cooling duct as far asthe opening of the connection piece, where it forms the deflectionsurface for the cooling medium. To improve the transition between theconnection piece and the cooling duct from the flow point of view, it isalready sufficient that the deflection surface is formed by a bevelledend of the formed piece. Deflection surfaces optimised from the flowpoint of view with a concave curvature naturally permit furtherreduction of the local pressure loss.

The formed piece may also be a prefabricated transition piece, e.g. acopper mould casting, which is inserted sealed from the outside in asuitably adapted recess in the cooling plate body, into which thecooling duct forms an opening. This transition piece has a curvedinternal transition duct, which forms a first and second opening in thetransition piece. The first opening terminates in the connection piecein this case. By contrast the second opening in the cooling plate bodyis opposite the opening of the cooling duct. The curved transition duct,which may be integrally, cast in a mould casting, for example, forms atransition substantially more favorable from the flow point of view fromthe connection piece to the cooling duct than a pipe connection weldedor soldered directly into a hole in the cooling plate body.

These cooling plates with inserted transition pieces likewise have theadvantage that the transition between the connection piece and thecooling duct is always formed identically by a standardizedprefabricated transition piece, so that the pressure losses in theindividual cooling circuits can be predetermined and coordinated farmore easily. The transition pieces are also preferable from themechanical point of view to direct welding or soldering in of aconnection piece into a hole in the cooling plate body.

Reduction of the pressure loss by the transition piece according to theinvention is particularly pronounced for cooling plate bodies withcooling ducts, which have an oblong cross-section. In these coolingplates the transition from the oblong cross-section of the cooling ductto a circular cross-section in the coolant connection is in facteffected progressively in the curved transition duct of the transitionpiece, so that discontinuities in the flow pattern are avoided.

The transition piece advantageously has a solid shoulder, which forms aspacer which projects from the back of the cooling plate. In theassembled cooling plate these shoulders simultaneously press a seal intothe bushing of the connection pieces in the furnace shell. It is thusunnecessary to weld or solder an additional element around theconnection piece to the back of the cooling plate, so that the coolingplate production process is simplified. Furthermore, a relatively solidshoulder on the transition piece facilitates assembly of the connectionpiece.

The recess for the transition piece is advantageously cut into thecopper cooling plate body from the rear, the depth of the recess beingsmaller than the thickness of the cooling plate body. With thisembodiment the front side of the cooling plate facing the furnaceinterior remains intact.

The recess for the transition piece advantageously terminates in one endof the cooling plate body. Consequently it can be manufactured moreeasily and the cooling duct can extend to a point immediately adjacentto the end of the cooling plate body. Furthermore, it should be noted inrelation to this embodiment of the invention that the transition piececloses and seals the cooling duct at the end. Consequently the solderingor welding of plugs into the cooling ducts open at the ends described inDE-A-2907511 and WO98/30345 is dispensed with, so that a furtheroperating step is saved.

In a first embodiment the cooling plate body is a forged or rolledcopper ingot as described in DE-A-2907511, the cooling ducts beingproduced as blind holes by mechanical deep drilling.

In a preferred embodiment the copper cooling plate body is continuouslycast as described in WO98/30345, however, the cooling ducts beingproduced as through ducts in the casting direction during continuouscasting.

Production of such a cooling plate is particularly simple, but it stillhas far better mechanical and thermal properties than a cast coppercooling plate.

BRIEF DESCRIPTION OF THE DRAWINGS

For better illustration of the invention and its advantages, anexemplified embodiment will be described in more detail with the aid ofthe enclosed drawings.

FIG. 1 shows a plan view of the rear of a cooling plate according to theinvention;

FIG. 2 a perspective section of the cooling plate in FIG. 1;

FIG. 3 a perspective detailed view of a transition piece with connectionpiece;

FIG. 4 a perspective detailed view of the transition piece in FIG. 3inserted in an end recess in a cooling plate body;

FIG. 5 a section through an alternative embodiment of a cooling plateaccording to the invention in the area of the transition between coolingduct and connection piece;

FIG. 6 a view of a formed piece for the embodiment of the transitionbetween cooling duct and connection piece as shown in FIG. 5.

FIG. 1 shows a cooling plate 10 for a shaft furnace, in particular ablast furnace. Such cooling plates, also known as “staves”, are arrangedon the inside of the furnace shell and connected to the furnace coolingsystem. The back 11 of the cooling plate 10 shown in FIG. 1 is oppositethe furnace shell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The cooling plate 10 shown consists essentially of a cooling plate body12 made from copper or a copper alloy with a rectangular surface. Fourstraight cooling ducts 14, which extend parallel with the surfacethrough the cooling plate body 12 from one end 16 to the opposite end18, are integrated in the cooling plate body 12. This cooling plate body12 was advantageously manufactured by the method described in thesubsequently published patent application WO 98/30345. A preform of thecooling plate body 12 was continuously cast in a continuous castingmould, whereby rod-type inserts in the casting duct produced ductsrunning in the casting direction, which form the cooling ducts 14. Asshown in FIG. 2 the cross-section of the integrally cast ducts 14 has anoblong shape with its smallest dimension at right angles to the plate. Aplate was cut out of this continuously cast preform by two cuts at rightangles to the casting direction, the two end faces 16 and 18 of thecooling plate body 12 being formed. Grooves 19 running at right anglesto the longitudinal direction of the plate were subsequently cut intoone of the two surfaces of the cooling plate body 12 (see FIG. 2). Thissurface with the cut grooves 24 forms the front side 25 of the coolingplate body 12, which faces the furnace interior. After assembly of thecooling plate 10 in the blast furnace, the front side 25 of the coolingplate body 12 can be provided with a refractory material, the grooves 19ensuring better adhesion of the refractory material.

On the back of the cooling plate 10 each cooling duct 14 has aconnection piece 20 or 22 at each end. These connection pieces 20, 22are essentially at right angles to the surface of the cooling plate body12. They are led through the furnace shell to the outside of thefurnace, where they are connected to the connection pieces of anadjacent cooling plate, so that the cooling plate 10 is incorporated inthe cooling circuit of the furnace shell. The connection pieces 20serve, for example, as feed connections and the connection pieces 22 asreturn connections of the cooling plate 10.

The connection according to the invention of connection pieces 20, 22 tothe cooling ducts 14 in the cooling plate body 12 is described in moredetail with the aid of FIGS. 2 to 4. FIG. 3 shows a transition piece 24,which is used for this connection according to the invention. It isadvantageously a copper or copper alloy mould casting. As the thermalconductivity of the material used for manufacture of the transitionpiece 24 is not significant, a copper alloy suitable for mould casting,for example, and with higher mechanical strength than the copper alloyof the cooling plate body can be selected. The latter should in fact becharacterized mainly by good thermal conductivity. The one-piecetransition piece consists of a prismatic base 26 with two rounded edges28, 30 and a cylindrical shoulder 32. The connection piece 22 is welded,soldered or screwed into a hole in the shoulder 32 or cast at the sametime and projects at right angles from the free surface 33 of thisshoulder 32. The inside diameter of this hole corresponds essentially tothe outside diameter of the connection piece 22. A curved transitionduct 34 is internally cast in the mould casting 24. This duct forms anopening 36 into the connection piece 22 in the shoulder 32, the openinghaving essentially the same circular free cross-section as theconnection piece 22. A second opening 38 in the transition duct 26 isarranged in a lateral area 40 of the prismatic base 26. This secondopening 38 has essentially the same oblong cross-section as the coolingducts 14 in the cooling plate body. The integrally cast transition duct34 is designed in such a way that the transition from the oblong to thecircular cross-section takes place progressively, i.e. withoutsignificant discontinuities, which would produce local vortices and thuspressure losses in the flowing cooling medium.

As shown in FIGS. 1, 2 and 4, a mould casting 24 is inserted with itsbase 26 in a suitable recess in the copper cooling plate body 12 at eachend of a cooling duct 14. These recesses are advantageously cut from therear into the copper cooling plate body, the rounded corners 28 and 30on the base 26 substantially simplifying this work. As shown in FIG. 4,each of the recesses terminates laterally in the respective end 16, 18of the cooling plate body 12, the depth of the recesses being smallerthan the thickness of the cooling plate body 12, so that the front ofthe cooling plate body 12 with its cut grooves 19 remains intact (seealso FIG. 4). The second opening 38 of the transition duct 34 in themould casting 24 is exactly opposite the opening of the cooling duct 14into this recess. The remaining gap between the cooling plate body andthe base 26 inserted in the recess is welded or soldered all round thesurface, so that no cooling medium can escape through this gap. FIGS. 2and 4 show that this seam has a relatively simple course, so that it canalso easily be applied mechanically.

As shown in FIGS. 2 and 4, the shoulders 32 project from the coolingplate body 12 as pressing elements, which press a seal into theconnection piece bushing in the furnace shell when the cooling plate isassembled.

As already mentioned above, the curved transition duct 34 integrallycast in the mould casting 24 forms a transition substantially morefavorable from the flow point of view from the connection piece 20, 22to the cooling duct 14 than a pipe connection piece welded or soldereddirectly into a hole in the cooling plate body. The pressure losses inthe cooling plate 10 are thus substantially reduced, which, of course,has a favorable effect on the energy consumption for circulation of thecooling medium. Furthermore the risk of steam bubble formation due tohigh local pressure losses at the transition from cooling duct toconnection piece is greatly reduced. The cooling plate 10 according tothe invention likewise has the advantage that the transition from theconnection piece 20, 22 to the cooling duct 14 is always effectedidentically by a standardized casting 24, so that the pressure losses inthe individual cooling circuits can be predetermined and coordinated farmore easily. The solution according to the invention is, of course,likewise preferable also from the mechanical point of view to directwelding or soldering of a connection piece into a hole in the coolingplate body. The solid shoulder into which the connection piece 20, 22 isinserted, makes a significant contribution in this respect.

Finally, it should be noted that the cooling plate body of a coolingplate according to the invention could also be manufactured by themethod with blind holes described in DE-A-2907511. However, productionby continuous casting as described above is far simpler and thereforealso preferable. Furthermore, the cross-section of the integrally castducts may have an oblong shape with its smallest dimension at rightangles to the cooling plate. Consequently the continuously cast coolingplates can be manufactured with a smaller plate thickness than coolingplates with drilled ducts, with the result that copper is saved and theuseful volume of the furnace is increased. The present inventionadvantageously reduces the higher pressure losses which occur withtransition to the connection piece 20, 22 with a circular freecross-section.

A simplified embodiment according to the invention of the transitionregion between the connection piece 20 and the cooling duct 14 is shownin FIG. 5. The connection piece is inserted directly in the coolingplate body 12 and welded to the latter. A formed piece 124, which isinserted in a recess 126 of the cooling plate body 12 in an axialextension of the cooling duct 14, forms a deflection surface 134 for thecooling medium in the area of the opening of the connection piece 20into the cooling duct 14. As shown in FIG. 6, the formed piece 124, forexample, is a plug, which is inserted in the end opening of the coolingduct 14 and extends to the opening of the connection piece 20 into thecooling duct 14. The deflection surface 134 for the cooling medium isformed by the front surface of its end 128 bevelled to 45°. As shown inFIG. 5, the cross-section of the duct 14 above the opening of theconnection piece 20 is slightly larger than the cross-section of theactual cooling duct 14. This forms a shoulder area 130 in the duct 14,on which a corresponding shoulder area 132 of the plug 124 rests, sothat the deflection surface 134 is positioned exactly below the openingof the connection piece 20 into the cooling duct 14.

In FIGS. 5 and 6, the cooling duct 14 and plug 124 have an oblongcross-section. However, both could, of course, have a circularcross-section.

1. A cooling plate for an iron- and steelmaking furnace comprising: acopper cooling plate body with at least one cooling duct for a coolingmedium, which extends essentially parallel with the back of said coolingplate body, and at least one preformed, externally accessible recessinto which said cooling duct opens; at least one connection piece for acooling medium connection on the back of said cooling plate body; and aformed piece that is fitted in said preformed, externally accessiblerecess in said cooling plate body so as to form a deflection surface forthe cooling medium flowing from said connection piece into said coolingduct or from said cooling duct into said connection piece in axialextension of said connection piece.
 2. The cooling plate according toclaim 1, wherein said formed piece is arranged in an axial extension ofsaid cooling duct, said deflection surface being formed by one of itsend faces in axial extension of said connection piece.
 3. The coolingplate according to claim 2, wherein: said cooling plate body has a frontside, a rear side and an end face; said recess axially extends saidcooling duct into said end face; said connection piece opens from saidrear side into said cooling duct; said formed piece is a plug, which isinserted from said end face into said recess and extends to the areawhere said connection piece opens into said cooling duct to form saiddeflection surface for said cooling medium in axial extension of saidconnection piece.
 4. The cooling plate according to claim 3, whereinsaid plug has a bevelled end which forms said deflection surface.
 5. Aprocess of manufacturing a cooling plate for an iron- and steelmakingfurnace comprising following steps: manufacturing a cooling plate bodyfrom copper or a copper alloy with at least one cooling duct for acooling medium, which extends essentially parallel with the back of saidcooling plate body, and at least one externally accessible recess intowhich said cooling duct opens; providing at least one connection piecefor a cooling medium connection on the back of said cooling plate body;and fitting a formed piece in said preformed, externally accessiblerecess in said cooling plate body so as to form a deflection surface forthe cooling medium flowing from said connection piece into said coolingduct or from said cooling duct into said connection piece in axialextension of said connection piece.
 6. The process according to claim 5,wherein said formed piece is arranged in an axial extension of saidcooling duct, said deflection surface being formed by one of its endfaces.
 7. The process according to claim 6, wherein: said cooling platebody has a front side, a rear side and an end face; said recess axiallyextends said cooling duct into said end face; and said connection pieceopens from said rear side into said cooling duct. said formed piece is aplug, which is inserted from said end face into said recess and extendsto the area where said connection piece opens into said cooling duct toform said deflection surface for said cooling medium in axial extensionof said connection piece.
 8. The process according to claim 7, whereinsaid plug has a bevelled end, which forms said deflection surface.